The long-range purpose of this project is to increase our understanding of the basic mechanisms of electrolyte movement across the endolymph-perilymph barrier in the guinea pig cochlea under normal conditions and under the influence of physical and chemical agents. The aim of the current project is: 1) to reveal electrolyte movement (Na ion, K ion and Cl ion) across the endolymph-perilymph barrier after exposure to intermediate levels of noise and 2) to correlate alteration of the ionic permeability of the cochlear partition with changes in sensitivity of the auditory system.